Breakup

My ex bf and me broke up a couple of days ago it was mutual I guess a 5month relationship we just clicked at the start we were so in love then.. we would speak for hours and talk about the future ALOT and he would tell me how much he loves me and stuff all the time at the start he would be obsessed with me I would play hard to get but towards the end.. the spark went I deleted him of everything we decided its best not to be friends but I see him around EVERYDAY I walk past him he looks at me touches his hair and if hes with a girl he makes sure I see.. I'm still in love with him hes leaving in a month though so is it best to just leave us seperated? And how should I react when I see him or walk past him? How do I make him miss me